It has become common practice to perform well service operations, such as formation testing and evaluation, using pressure controlled valve devices such as those shown in the Nutter U.S. Pat. No. Re 29,638 patent issued May 28, 1978 and assigned to the assignee of this invention. Other related devices are illustrated, for example, in Nutter U.S. Pat. Nos. 3,823,773 issued July 16, 1974, and 3,986,554 issued Oct. 19, 1976, as well as in my U.S. Pat. Nos. 4,403,659 issued Sept., 13, 1983, 4,479,242 issued Oct. 2, 1984, and 4,576,234 issued Mar. 18, 1986, all assigned to the assignee of this invention. All of these devices are valve structures that are operably responsive to changes in the pressure of fluids that stand either in the tubing-to-casing annulus, or in the tubing. These tools have been used quite successfully in testing cased well bores where a high level pressure signal can be applied safely to the annulus fluids. However some very deep, cased wells are not tested with pressure controlled tools because the operating pressure might exceed the burst rating of the casing. Moreover, testing in open (uncased) boreholes has not been done with standard pressure controlled tools for fear that operating pressures might break down the exposed formations and cause damage to their productive capabilities. Certain types of valve devices, such as circulating valves, have required comparatively long operating times due to the complicated series of annulus or tubing pressure changes that are required to cycle the tool from closed to open position, and to reclose it, if desired. Inherent in such designs has been increased length, to the point where a typical combination of tester, sampler and circulating valves might well have an overall length in excess of 100 feet. Of course increased complexity of valve systems generally reduces reliability, and increases the chances of misruns. Nevertheless, there is a continuing need in this industry to increase the number of service operations that can be performed downhole in a single trip of the well testing tool string into the well. With the foregoing limitations and industry needs in mind, I have invented the downhole tool control system disclosed and claimed in this application.
A general object of the present invention is to provide a new and improved control system for downhole pressure operated tools that is operably responsive to low level pressure change signals, as thus has application to all types of wells including deep cased wells and open hole.
Another object of the invention is to provide a new and improved downhole device control system that includes a power source and command module which enables numerous sequences of valve operation to be performed on a single run.
Another object of the present invention is to provide a new and improved remote controlled downhole valve system that does not require long operating times or a complicated sequence of annulus or tubing pressure applications.
Still another object of the present invention is to provide a new and improved pressure responsive well testing tool that has a relatively short length, and which is simple and reliable in operation.